Visionary transparent memory a step closer to reality

HOUSTON – (Oct. 2, 2012) – Researchers at Rice University are designing transparent, two-terminal, three-dimensional computer memories on flexible sheets that show promise for electronics and sophisticated heads-up displays.

The technique based on the switching properties of silicon oxide, a breakthrough discovery by Rice in 2008, was reported today in the online journal Nature Communications.

The Rice team led by chemist James Tour and physicist Douglas Natelson is making highly transparent, nonvolatile resistive memory devices based on the revelation that silicon oxide itself can be a switch. A voltage run across a thin sheet of silicon oxide strips oxygen atoms away from a channel 5 nanometers (billionths of a meter) wide, turning it into conductive metallic silicon. With lower voltages, the channel can then be broken and repaired repeatedly, over thousands of cycles.

That channel can be read as a "1" or a "0," which is a switch, the basic unit of computer memories. At 5 nm, it shows promise to extend Moore's Law, which predicted computer circuitry will double in power every two years. Current state-of-the-art electronics are made with 22 nm circuits.

The research by Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science; lead author Jun Yao, a former graduate student at Rice and now a post-doctoral researcher at Harvard; Jian Lin, a Rice postdoctoral researcher, and their colleagues details memories that are 95 percent transparent, made of silicon oxide and crossbar graphene terminals on flexible plastic.

The Rice lab is making its devices with a working yield of about 80 percent, "which is pretty good for a non-industrial lab," Tour said. "When you get these ideas into industries' hands, they really sharpen it up from there."

Manufacturers who have been able to fit millions of bits on small devices like flash memories now find themselves bumping against the physical limits of their current architectures, which require three terminals for each bit.

But the Rice unit, requiring only two terminals, makes it far less complicated. It means arrays of two-terminal memories can be stacked in three-dimensional configurations, vastly increasing the amount of information a memory chip might hold. Tour said his lab has also seen promise for making multi-state memories that would further increase their capacity.

http://www.eurekalert.org/pub_releases/2012-10/ru-vtm100212.php